The overall goal of the proposed Arkansas Older Americans Independence Center (OAIC) is to promote the translation of basic and physiological research on cardiac and skeletal muscle dysfunction in aging and disease to clinically relevant outcomes that ultimately have a positive influence on the standard of care. A particular emphasis will be nutritional approaches to ameliorating the physiological impact of changes in muscle metabolism. The fundamental strategy centers on determining the metabolic basis for observed catabolic responses in order to design and test approaches to counteract these responses. Stable isotope tracer methodology is uniquely suited to advance this overall goal of the Arkansas OAIC. Stable isotope tracer methodology can be used in the most basic in vitro studies and in small animal studies to quantify metabolic reactions, and the same methodology can be extended to human studies. A number of clinical outcome studies have validated the success of acute tracer studies of muscle metabolism in predicting longterm outcomes (e.g., references. 1,2). Consequently, the Analytical Core's primary goal will be to support the performance of stable isotope tracer experiments, including sample and data analysis, and to continue to develop new methodologies, as needed, to support studies related to therapeutic nutrition and aging, with particular emphasis on issues related to skeletal and cardiac muscle dysfunction associated with aging and/or congestive heart failure (CHF), including the condition of cardiac cachexia. We will also actively train investigators on stable isotope tracer methodology.